Aphasia is the name given to a collection of language disorders caused by damage to the brain.
A requirement for a diagnosis of aphasia is that, prior to the illness or injury, the person’s language skills were normal (for developmental language disorders, see specific language impairment). The difficulties of people with aphasia can range from occasional trouble finding words to losing the ability to speak, read, or write, but does not affect intelligence. This also affects visual language such as sign language.
The term “aphasia” implies a problem with one or more functions that are essential and specific to language function. It is not usually used when the language problem is a result of a more peripheral motor or sensory difficulty, such as paralysis affecting the speech muscles or a general hearing impairment.